7,246 research outputs found
Rescattering effects in charmless B_{u,d,s} to P P decays
We study the final-state interaction (FSI) effects in charmless B_{u,d,s} to
PP decays. We consider a FSI approach with both short- and long-distance
contributions, where the former are from in-elastic channels and are contained
in factorization amplitudes, while the latter are from the residual
rescattering among PP states. Flavor SU(3) symmetry is used to constrain the
residual rescattering S-matrix. We fit to all available data on the CP-averaged
decay rates and CP asymmetries, and make predictions on unmeasured ones. Our
main results are as follows: (i) Results are in agreement with data in the
presence of FSI. (ii) For B decays, the pi^+pi^- and pi^0pi^0 rates are
suppressed and enhanced respectively by FSI. (iii) The FSI has a large impact
on direct CP asymmetries of many modes. (iv) The deviation (Delta A) between
A(B{bar}^0 to K^-pi^+) and A(B^-to K^-\pi^0) can be understood in the FSI
approach. (v) Sizable and complex color-suppressed tree amplitudes, which are
crucial for the large \pi^0\pi^0 rate and Delta A, are generated through
exchange rescattering. The correlation of the ratio B(pi^0pi^0)/B(pi^+pi^-) and
Delta A is studied. (vi) The B^- to pi^-pi^0 direct CP violation is very small
and is not affected by FSI. (vii) Several B_s decay rates are enhanced. In
particular, the eta'eta' branching ratio is enhanced to the level of
1.0X10^{-4}, which can be checked experimentally. (viii) Time-dependent CP
asymmetries S in B_{d,s} decays are studied. CP asymmetries in these modes will
be useful to test the SM.Comment: 33 pages, 6 figures, version to appear in Phys. Rev.
Interacting classical and quantum particles
We apply Hall and Reginatto's theory of interacting classical and quantum
ensembles to harmonically coupled particles, with a view to understanding its
experimental implications. This hybrid theory has no free parameters and makes
distinctive predictions that should allow it to be experimentally distinguished
from quantum mechanics. It also bears on the questions of quantum measurement
and quantum gravity.Comment: 7 pages, 6 figure
InGaN nano-ring structures for high-efficiency light emitting diodes
A technique based on the Fresnel diffraction effect for the fabrication of nano-scale site-controlled ring structures in InGaN/GaN multi-quantum well structures has been demonstrated. The ring structures have an internal diameter of 500 nm and a wall width of 300 nm. A 1 cm-1 Raman shift has been measured, signifying substantial strain relaxation from the fabricated structure. The 9 nm blueshift observed in the cathodoluminescence spectra can be attributed to band filling and/or screening of the piezoelectric field. A light emitting diode based on this geometry has been demonstrated
Evidence for Factorization in Three-body B --> D(*) K- K0 Decays
Motivated by recent experimental results, we use a factorization approach to
study the three-body B --> D(*) K- K0 decay modes. Two mechanisms are proposed
for kaon pair production: current-produced (from vacuum) and transition (from B
meson). The Bbar0 --> D(*)+ K- K0 decay is governed solely by the
current-produced mechanism. As the kaon pair can be produced only by the vector
current, the matrix element can be extracted from e+ e- --> K Kbar processes
via isospin relations. The decay rates obtained this way are in good agreement
with experiment. Both current-produced and transition processes contribute to
B- --> D(*)0 K- K0 decays. By using QCD counting rules and the measured B- -->
D(*)0 K- K0 decay rates, the measured decay spectra can be understood.Comment: 17 pages, 6 figure
Sampling rare fluctuations of height in the Oslo ricepile model
We have studied large deviations of the height of the pile from its mean
value in the Oslo ricepile model. We sampled these very rare events with
probabilities of order by Monte Carlo simulations using importance
sampling. These simulations check our qualitative arguement [Phys. Rev. E, {\bf
73}, 021303, 2006] that in steady state of the Oslo ricepile model, the
probability of large negative height fluctuations about
the mean varies as as with
held fixed, and .Comment: 7 pages, 8 figure
Phenomenological Consequences of Right-handed Down Squark Mixings
The mixings of quarks, hidden from view in Standard Model (SM), are
naturally the largest if one has an Abelian flavor symmetry. With supersymmetry
(SUSY) their effects can surface via squark loops. Squark and
gluino masses are at TeV scale, but they can still induce effects comparable to
SM in (or ) mixings, while mixing could be close to recent
hints from data. In general, CP phases would be different from SM, as may be
indicated by recent B Factory data. Presence of non-standard soft SUSY
breakings with large could enhance (or )
transitions.Comment: Version to appear in Phys. Rev. Let
Interplay between interfacial energy, contact mechanics, and capillary forces in EGaIn droplets
Eutectic gallium–indium (EGaIn) is increasingly employed as an interfacial conductor material in molecular electronics and wearable healthcare devices owing to its ability to be shaped at room temperature, conductivity, and mechanical stability. Despite this emerging usage, the mechanical and physical mechanisms governing EGaIn interactions with surrounding objects─mainly regulated by surface tension and interfacial adhesion─remain poorly understood. Here, using depth-sensing nanoindentation (DSN) on pristine EGaIn/GaOx surfaces, we uncover how changes in EGaIn/substrate interfacial energies regulate the adhesive and contact mechanic behaviors, notably the evolution of EGaIn capillary bridges with distinct capillary geometries and pressures. Varying the interfacial energy by subjecting EGaIn to different chemical environments and by functionalizing the tip with chemically distinct self-assembled monolayers (SAMs), we show that the adhesion forces between EGaIn and the solid substrate can be increased by up to 2 orders of magnitude, resulting in about a 60-fold increase in the elongation of capillary bridges. Our data reveal that by deploying molecular junctions with SAMs of different terminal groups, the trends of charge transport rates, the resistance of monolayers, and the contact interactions between EGaIn and monolayers from electrical characterizations are governed by the interfacial energies as well. This study provides a key understanding into the role of interfacial energy on geometrical characteristics of EGaIn capillary bridges, offering insights toward the fabrication of EGaIn junctions in a controlled fashion
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